From: John Stone (
Date: Tue Apr 06 2004 - 09:57:04 CDT

  Why not draw two triangles to make your quadrilateral?
That's what the OpenGL accelerator would do with a quad anyway.
Same approach works for any polygon of course, though getting nice
results requires making an intelligent decisions when decomposing
polygons with large numbers of vertices into triangles that will yield
good results in depth testing, shading, etc. For a quadrilateral its
quite simple however.

  John Stone

On Tue, Apr 06, 2004 at 01:39:54PM +0200, Vlad Cojocaru wrote:
> Dear VMD users,
> I would like to draw a closed rectangle connecting 4 atoms. I know
> that a triangle is very easy to draw using graphics or draw tcl commands
> but I did not find the same features for drawing higher order poligons.
> Could somebody give me a hint.
> I dont want to use the draw line command and draw 4 lines because I
> would like to have a color filled rectangle.
> Furthermore I would be interested if VMD has the ability to calculate
> a dihedral angle between two planes which are defined by two such
> rectangles?
> Thank you very much in advance
> Best wishes
> Vlad
> --
> Vlad Cojocaru
> Max Planck Institute for Biophysical Chemistry
> Department: 060
> Am Fassberg 11, 37077 Goettingen, Germany
> tel: ++49-551-201.1327
> e-mail:
> home tel: ++49-551-9963204

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